Advances in switched-current techniques for analogue signal processing

The main advantage of the switched-current technique, when compared to switched-capacitors, is its compatibility with digital VLSI technology. This makes the technique particularly well suited to mixed-mode applications, such as sigma-delta and algorithmic converters. The switched-current memory cell (also known as the current copier) was initially conceived to overcome the inherent matching limitations of continuous time current mirrors. Initially, the cell found application in high performance D/A converters and more recently as a delay element for the realisation of analogue filters. The practical utility of switched-current techniques for filter design has been demonstrated by fabricated filters. In this paper the authors review existing class A and class AB switched-current techniques, show fabricated results for the class A cell and explore several potential areas of application in the face of digital VLSI technology